ERK1/2介导糖基转移酶GnT-III调控内质网稳态在AD中作用及机理

In recent years, it has been found that the abnormal glycosylation may play an important role in the pathogenesis of Alzheimer’s disease (AD). In 2018, our research group also found and reported that the levels of bisecting GlcNAc and N-acetylglucosaminyltransferase III (GnT-III), which is responsible for synthesizing a bisecting GlcNAc residue, were increased in AD animal and cell model. We further revealed that ERK1/2 may be closely associated with GnT-III, but the specific role of GnT-III in AD and the mechanism of its action on ERK1/2 are still unclear and require further study. Therefore，in this project, to confirm the role of GnT-III in AD, we will firstly establish AD cells and animal model and use different means to intervene GnT-III, such as RNAi, miRNA, mutation of enzyme active site, gene knockout. Secondly, we will analyze the role of destroyed endoplasmic reticulum homeostasis caused by abnormal protein N-glycosylation in GnT-III mediated AD pathogenesis. Thirdly, we will further explore the definite interplay of GnT-III and ERK1/2, and clarify the molecular mechanism of GnT-III and ERK1/2 interplay through regulating GnT-III and ERK1/2 signaling pathway respectively. The aim of this project is to explain the role and mechanism of GnT-III in AD, and provide new experimental and theoretical basis for the potential targets in AD.

近年研究发现异常糖基化修饰可能在阿尔兹海默病（AD）中至关重要，本课题组也发现并于2018年报道了AD动物细胞模型中平分型N-糖链及负责其合成的N-乙酰氨基葡萄糖转移酶III（GnT-III）异常增加，且进一步研究发现神经细胞中ERK1/2可能与GnT-III紧密关联，但GnT-III在AD中具体作用及其作用于ERK1/2的机理尚不清楚，亟待确证和深入研究。基于此，本项目首先在AD动物细胞模型建立的基础上，采用RNAi、miRNA、酶活性位点突变、基因敲除等手段分别干预，确证GnT-III在AD中作用，解析蛋白N-糖基化异常介导内质网稳态失调在GnT-III作用于AD中地位；进一步，深入探讨GnT-III与ERK1/2之间具体作用方式，同时，分别通过调控GnT-III及ERK1/2信号轴阐释其相互作用分子机理。明确GnT-III在AD中的作用及机制；为治疗AD的潜在靶标提供实验和理论基础。

本课题组前期发现并报道了GnT-III在APP/PS1小鼠中异常上调，但是GnT-III在AD中的具体功能及其对AD的调控机制尚不明确。本项目首先建立不同AD动物模型及衰老小鼠模型，明确GnT-III在AD及衰老小鼠脑内表达水平的变化。随后在正常小鼠与AD小鼠脑内过表达GnT-III，发现过表达GnT-III导致小鼠出现认知功能障碍并且加剧AD小鼠的认知异常与脑内淀粉样斑块沉积情况。进一步使用MGAT3 shRNA，D321A与miRNA在AD小鼠脑内干预GnT-III表达或使其功能失活，发现干预GnT-III可显著缓解AD小鼠认知障碍与脑内病理水平。深入分析GnT-III调控AD的分子机制，发现GnT-III通过与ERK1/2直接结合或者通过其上游激酶MEK1/2进一步调控ERK1/2，确证了ERK1/2在GnT-III调控AD进程的关键作用。同时，探讨GnT-III对AD模型中内质网应激水平的影响，发现GnT-III干预或功能失活可明显缓解AD小鼠的内质网应激异常。提示靶向干预GnT-III对AD具有防治作用。. 本项目从细胞与动物水平探讨了GnT-III在AD中的功能及其调控机制，为AD的防治提供潜在靶点和研究基础。通过本项目，已发表论文14篇（SCI 论文10篇），培养研究生6名，其中博士研究生2名，硕士研究生 4 名。